There is a trend of new wind turbine models having increased rated power, and this increases the sizes of the turbines. The total weight of some modern offshore wind turbines amount to hundreds of tons, and in some cases the total weight of the blades only exceed a hundred tons.
Normally, before wind turbines are installed, their components, such as towers, blades and nacelles, are manufacturing at separate factories, after which the components are transported to the wind turbine erection sites. In addition some components, like towers, can be transported separated into sub-components, for example tower sections, from factories to assembly sites, at which the sub-components are assembled into components which are sent to the installation sites. Wind turbine tower sections are usually assembled by bolting flanges at the tower section ends together.
Transportation of wind turbine components usually takes place on roads, on railroad or at sea. The increasing sizes of wind turbine models mean that the sizes of their components increase as well. This causes challenges to their transportation.
For transport of wing turbine tower sections, a transport frame can be bolted onto the flange at each tower section end; DE202012009278U1 shows an example of such a frame. WO2007093854A2 discloses an example of an alternative device to be mounted to tower section flanges for tower transport. Similarly, for blades a transport frame can be bolted onto a flange at the blade root end, and another frame can be mounted somewhere between the tip of the blade and the blade centre of gravity.
Stacking components on top of each other can be useful to save floor space on the transporting vehicle or vessel, and to increase carrying capacity. For example, towers sections for a plurality of towers, or blades for a plurality of wind turbines, can be stowed on the deck of a sea vessel, or onto a train. Thereby, frames of the type mentioned above can be used for stacking the tower sections or the blades on top of each other. Examples of such stacking for tower sections are shown in EP2360372A1, US2008232920A1, WO2007093854A2 and WO2010012280A1, and for blades in WO2011076238A1.
Moving wind turbine components onto or off from a vessel or a vehicle is usually done with a crane. Also stacking of wind turbine components is usually done with a crane. Due to the increasing sizes of the components, large capacity cranes are needed at the site at which handling takes place. This adds to the complexity and planning of the transport handling procedures. In particular, the large cranes with the capacity needed for some wind turbine components might cause ground capacity problems, for example at harbour quays for loading components onto a sea vessel.
A way to avoid cranes when loading components onto or off from a vessel (e.g. a sea vessel) or a vehicle (e.g. a road truck or a railway vehicle) is to use a roll-on-roll-off system, i.e. a system where support devices with wheels are secured to the transported components, and the components with the support devices are rolled onto or off from vessel or vehicle. For example, a sea vessel can be provided in the form of a roll-on-roll-off ship (RoRo ship), which has a loading area which is accessible from a quay and allows the cargo to be rolled on and off the ship.
A problem with roll-on-roll-off systems is that they do not allow for stacking components without the use of a crane. However, as stated cranes can entail added complexity and planning of the transport handling procedures.
The discussion above focuses on transportation of wind turbine components, but similar considerations and problems can appear for storing wind turbine components.